Certain patients develop systemic reactions to stinging hymenoptera insects yet fail to have positive skin tests. This could be due either to improper testing antigens (whole body extracts), or that the reaction is not always IgE (reagin) mediated. Whole and fractions of pure venoms will be used for skin testing specific immunotherapy. Pre and post therapy sera and cells will be studied by several immunologic techniques to measure humoral and cellular response. Non-immunologic reactions (if such exist) may be due to deficiencies of inhibitors in man responsible for the destruction of pharmacologically active substances in the venom. Assay of these inhibitors in the sera and/or white cells will be studied.